For a number of years laser beams have been used in fabrication systems, operating on an object such as a substrate, for such purposes as drilling, fusion, or ablation of the object. In order to reduce the time of fabrication, the systems may use multiple laser beams, and the requirements for the accuracy of such multi-beam systems is constantly increasing.
U.S. Pat. No. 6,615,099 to Müller et al., whose disclosure is incorporated herein by reference, describes a process for calibrating a laser processing machine, operating using a “deflection device.” The process first generates an image of a calibration plate to determine imaging errors caused by the deflection device. The calibration plate is replaced by a test plate, upon which a test pattern is written and measured to determine an optical offset. Workpieces are processed in the machine by compensating for the imaging errors and the optical offset.